"PRINCIPLES OF PHYLOGENETICS: ECOLOGY AND EVOLUTION" Integrative Biology 200B Spring 2009 The Fossil Record and Dating: “How fast, as a matter of fact, do animals evolve in nature? That is the fundamental observational problem of tempo in evolution. It is the first question the geneticist asks the paleontologist. Some attempt to answer it is a necessary preliminary for the whole consideration of tempo and mode.” (Simpson 1944, p. 3) 1. Getting into the fossil record2. Assigning dates to fossils SHRIMP = sensitive high-resolution ion microprobe (U-Pb) IDTIMS = isotope dilution analysis using thermal ion mass spectrometry (U-Pb) U-Pb = Uranium Æ Lead Ar-Ar = 40Argon Æ 39 Argon Rb-Sr = rubidium-strontium fission track At Cambrian boundary (542 Ma) IDTIMS dates providing dates at error levels of ± 0.3 Ma. 3. Why do molecular clock dates oftenindicate earlier divergence dates? The Signor-Lipps
View Full Document
Unlocking...